The objective of this study is to determine the mechanism (s) by which an investigational new drug glimepiride, a sulfonylurea, improves glycemic control in NIDDM with specific reference to post absorptive glucose homeostasis. Glimepiride is thought to act by improving both insulin secretion and insulin sensitivity. Diabetic and normal subjects will have overnight hepatic glucose production, hyperglycemic clamp and euglycemic clamp studies done before and after four months of glimepiride.